1. Field
One or more embodiments of the present invention relate to an acoustic system, and more particularly, to a method and apparatus for measuring a distance to a sound source by using a microphone array.
2. Description of the Related Art
There are various application fields for technology which measures a distance to a sound source by only using an input to a microphone. When a distance to a speaker is known, a volume of a speaker can be regulated according to the distance so that the speaker can be heard well. In addition, during recording, an input-gain of a microphone can be appropriately regulated according to the distance to a speaker. In regulating an input-gain of a microphone based on a volume level, a speaker's voice cannot be heard if there is a large amount of ambient noise. However, if the distance to the speaker is known, an input-gain of a microphone can be regulated according to the distance.
In addition, a map indicating a location of a sound source can be drawn. Here, when a direction of and a distance to a sound source are known, which sound source is located in which location can be measured. In other words, the location generating noise can be determined. In addition, if information on the distance to a sound source is known, such information can be used to classify a sound source according to the distance. Moreover, various signal processing technologies using a distance can be applied to devices with microphones.
When a number of sound sources are mixed, technologies for removing only a sound source that is not desired, picking out only a desired sound source, and grouping according to the sound sources, use various sound source characteristics.
When noise can be easily detected, noise is removed using noise subtraction from sound in which noise and desired sound sources are mixed so that the desired signals remain. Also, when statistical characteristics of the sound sources are different to each other, a sound sources classifying method using the statistical differences of the sound sources, is used.
In addition, in the case of using geometrical characteristics of the sound sources, when the directions between the sound sources are different, only a sound source which can be heard from where the desired sound exists can be detected using a beam-forming technology. In addition to the directions, the distance between a sound source and a microphone is also important as geometrical characteristics of the sound sources.
As a method of obtaining the distance between the sound source and the microphone, a technology for calculating the distance between the sound source and the microphone, by using a level difference between a reference microphone and other microphone and an arrival time difference is disclosed. However, in such a method, an attenuation rate according to a distance to a general microphone is used and thus sensitivity according to the distance decreases. Moreover, if the distance of the sound source is to be used in signal processing at a back end, the distance should be measured based on frequency so that more detailed information can be provided. However, the distance based on the frequency cannot be measured using the method described above.